The present invention relates to a method for the local joining of stacked metal foils in strip form by electric pressure welding at both ends of the foil stack, with welding electrodes for conducting a welding current through the region of the foil stack to be joined together, as well as with a device for removing heat from the foil stack.
Flexible current-carrying ribbons fabricated in accordance with such a method are frequently employed especially in electrotechnology where parts movable relative to each other are to be connected to each other electrically. Fields of application of such current-carrying ribbons are therefore primarily all kinds of power circuit breakers and switching systems. The metal foils are connected to each other by pressure welding mechanically and in an electrically conducting manner, so that it is assured when a terminal connection is made that the current to be transmitted is distributed uniformly over all metal foils.
As materials for fabricating such current-carrying ribbons of metal foil can be considered particularly the conductor materials copper and aluminum, which are generally used in electrotechnology. Considering that the mobility of the parts to be joined together should be impeded as little as possible, it is necessary to use resilient metal foils. The difficulty arises here that aluminum as well as copper have by nature only insufficient spring properties and it is therefore necessary to subject the foils to a rolling treatment in order to give sufficient spring hardness to the material. If, however, the foils are subjected to temperatures above the recrystalization temperature, they lose their springness. In order to prevent this influence in the manufacture of current-carrying ribbons of foil stacks as far as possible, pressure welding has heretofore been performed in a water bath, since thereby the heat influence of pressure welding remains substantially limited to the pressure areas of the welding electrodes.
In a flame welding method, it is already known to use indirect cooling instead of a water bath. To this end, a liquid coolant is conducted through cavities in holding jaws, between which the parts to be welded together are clamped (British Pat. No. A-210,130).